In U.S. Pat. No. 3,291,947, issued Dec. 13, 1966 to Roswell C, Van Sickle, and assigned to the assignee of the instant application, there is described the function, purpose and desirable ohmic values of a closing resistance, which is inserted into the circuit only during the closing operation of the breaker, and which is out of the circuit, that is, shorted out of the circuit, during the opening operation of the breaker. In this U.S. Pat. No. 3,291,947, there is illustrated a rotating bridging type of separable main contact structure with an auxiliary resistance contact associated with each stationary contact, so arranged that the closing resistance, of a desirable specified ohmic value, is inserted into the controlled circuit at a predetermined time during the closing operation, and is ultimately shorted out in the fully-closed-circuit position of the interrupter.
During the opening operation of the aforesaid circuit-interrupter, as described in the aforesaid Van Sickle U.S. Pat. No. 3,291,947, the arrangement is such that the closing resistance is out of the circuit during the opening operation, and the extinguishing action, or arc interruption, occurs only at the separable rotating main contact structure and not at the closing-resistance contacts, which obviously is desirable.
In the aforesaid Van Sickle U.S. Pat. No. 3,291,947, there is claimed ranges of ohmic resistance values, which have been found to damp, or to entirely eliminate undesirable voltage surges on the controlled line during the closing operation of the circuit-interrupter. This is desirable inasmuch as the existence of high-voltage surges on the controlled line imposes unnecessary voltage stress on the insulation equipment of the line, and creates the concurrent hazard of flashover across such supporting insulating structures or equipment.